This information focuses on the RF Radio Frequency Interference reason for Grounding. Here is a article and pictures that demonstrates RF interference and multipath shielding grounding.
http://www.prism.gatech.edu/~wn17. In the same way putting the antenna in a grounded shield improves reception. Grounding the outer shied of coax cable with a coax ground block diverts part or all of interfering , electric noise , RF noise , electronic noise , multipath , atmospheric static , that is 'picked up' by the shied and shield wires directs/diverts the interference to ground and this improves reception.